Mipmaps look terrible in BGE standalone player. Can this be fixed?
When you let the BGE automatically generate the mipmap-textures it will partially result in blurred images. I do not know if there are parameters that can help generate better mipmaps.

To avoid automatic generation you can create your own mipmap textures and provide it in a dds texture file. You can create them with GIMP (DDS plugin). The drawback is the additional work. The advantage is that you do not need to do that for all objects, just the objects where the automatic mipmap generation is not sufficient.